When a celebrity returns to a talk show as a guest, there is usually fun chemistry with the host. However, that comfort isn't always there when the celebrity in question is making their first appearance.

When Jimmy Fallon began hosting The Tonight Show, he was beginning a new chapter of his career after becoming a household name on Saturday Night Live. This meant that a lot of celebrities were appearing on his show for the first time.

While Fallon has had many enjoyable interviews over the years, there were several celebrities whose first appearance on his show were anything but. One of them included Shawn Mendes, who got an embarrassingly quiet reception after a quip he made about Fallon's age.

Jimmy Fallon Couldn't Match Cardi B's Energy And Seemed Uncomfortable During Her First Appearance On The Show

When Cardi B first appeared on The Tonight Show in 2017, Fallon seemed ill-prepared for her energy. At first, it seemed that the host didn't understand her sense of humor.

The interview started with Cardi B making her signature noises, which Fallon appeared to ignore at first. Fallon asked Cardi B about her upbringing in the Bronx, leading the rapper to make her signature "Eeeoooow" sound. Fallon was then silent for a moment before taking a sip of water.

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One Twitter user reacted to the appearance, writing, "So entertaining for Cardi, but awkward for Jimmy."

As the interview went on, the two fell into a pretty comfortable groove with each other. She talked about her engagement to rapper Offset.

"He always used to tell me, ‘I’m gonna marry you!’ and it’s just like, ‘Hm, it’s the right thing to do,'" she said. "I knew he was going to give me a really expensive gift because he wasn’t there for my birthday. But I thought he was going to give me a watch or something, but he just went out his way. OK?"

Related: Jimmy Fallon Couldn't Keep Up With Cardi B And Was Noticeably Uncomfortable At The Start Of Their Interview

She also talked about her Grammy nominations for "Bodak Yellow," saying that while she was nervous, she already felt like a winner.

"I am nervous. You wanna know something? I already feel like a winner, you know what I’m saying? Because, it’s just like, I never thought, me!" she said. "Like, I already won. What’s good?"

Cardi B's rapport with Fallon developed so well, she even co-hosted an episode with him the following year.

Pete Davidson Swore So Much During His First Appearance, Fallon Jokingly 'Fired' Him During The Interview

When Pete Davidson made his first appearance on The Tonight Show in 2018, he was engaged to Ariana Grande. The engagement made headlines and caused Davidson's celebrity profile to increase significantly.

During the chat with Fallon, Davidson gushed about Grande and their relationship. However, things started to get weird when Fallon suggested the two get married on The Tonight Show.

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"Why do people care? It's very weird. It's weird 'cause like the president's like trying to pardon himself and he's like f****** a porn star," Davidson said, referring to Trump's alleged affair with Stormy Daniels.

While the audience responded with some decent laughs, Fallon seemed to get very uncomfortable. Davidson continued to use profanity throughout the rest of the interview. This caused Fallon to tell Davidson that he couldn't use words like that on television and jokingly "fired" him from the show.

"No it's fine, I'll go on Seth [Meyers' show], I don't give a s*** ... I actually have Seth's number, I don't have your number," Davidson said.

"And you're never gonna get it either," Fallon responded to a shocked reaction from the audience.

Obviously, the exchange didn't prevent Davidson from being invited back to the show in the future. In 2019, Davidson made another appearance on the show and told Fallon he was trying to find a new name for his man cave. He also spoke about living with his mother and playing Mortal Kombat 11.

Related: Jimmy Fallon Almost Banned A Popular Guest From Appearing On The Tonight Show After His Profanity-Ridden Interview

In 2021, Davidson told Fallon about the time he and Machine Gun Kelly fell off the SNL stage during the credits when Kelly tried to pick him up.

"He got really excited and he went to pick me up, and he forgot he had a bruised coccyx," Davidson explained. "So he went to pick me up and he couldn't go up, so he just started to slowly tilt back."

Shawn Mendes Likens Fallon To His Grandfather And It Leads To Another Uncomfortable Moment

When Shawn Mendes appeared on The Tonight Show for the first time in 2016, he helped Fallon with a #FallSongs segment. The segment involved Mendes singing other people's tweets. Mendes sang the first tweet to the tune of his hit "Stitches."

However, things got a little uncomfortable when Mendes sang the second tweet. Mendes appeared to be dissatisfied with the second song, complaining that Fallon gave him a late cue. This caused Mendes to make several jokes about Fallon's age.

The audience was laughing at first, but things soon came to a deafening silence when Mendes said, "You sound like my grandfather."

Despite this, Mendes was invited back on the show. However, in 2018, the singer had another uncomfortable moment with Fallon.

Mendes was talking about performing with Justin Timberlake at the 2018 iHeartRadio Music Festival. Fallon has shared a very public friendship with Timberlake which dates back to Fallon's days on Saturday Night Live.

Related: Jimmy Fallon Was One Of The Only Late Night Show Hosts That Got To 'Mess Up' Donald Trump's Hair During Their Interview

Because of this public friendship, Fallon began teasing Mendes about Timberlake liking him more. Mendes responded by saying that he and Timberlake are "pretty good friends now." However, as the banter continued, viewers seemed to feel the exchange got more and more awkward.

However, like Cardi B and Pete Davidson, Mendes was invited back many more times. Like Cardi B, he even co-hosted an episode of the show with Fallon.